Slubbing machines according to the present disclosure are often speed frames. A speed frame serves to manufacture roving yarn. Roving yarn may also be referred to as slubbing or roving. The roving yarn serves as the basis for the spinning process which includes the spinning of fibers into a fiber yarn, for example on a ring-spinning machine.
The process for manufacturing a roving yarn may include the following steps. First, the fiber bands coming from the preliminary process (carding room) are doubled with the aid of drafting devices and deposited in cans. The fiber assembly produced by this process is then presented to the stubbing machines for further processing. In these slubbing machines, the fiber assembly is first drawn through a drafting device and then slightly twisted by the application of a suitable twist. The fiber assembly is then wound up as a roving yarn on a supply bobbin. The roving yarn, also referred to as the fiber stubbing, the flyer slubbing, or generally as the slubbing, manufactured according to this process usually serves as presentation material for ring-spinning machines.
A slubbing machine usually includes its own drafting device. In most cases, this drafting device is a double apron drafting device. After being drawn through the drafting device, the fiber assembly undergoes a slight twist, also referred to as a protective twist, in order for the slubbing to exhibit sufficient strength to be wound on a bobbin without disintegrating. The twist must only be of sufficient strength for the fiber assembly to be held together for the winding and later unwinding of the fiber assembly and for the transport of the bobbins. The twist must also be sufficiently strong to avoid wrong draftings (thin places in the roving yarn). On the other hand, the twist must be easy to be released again so that the roving yarn is capable of being drawn for the subsequent spinning process, for example in a ring-spinning machine.
A speed frame is often used as a slubbing machine to manufacture flyer slubbing. The speed frame is equipped with a drafting device and a spindle for winding up the flyer slubbing onto a cylinder bobbin by means of a flyer which supports the slubbing against the centrifugal force incurred by the bobbin revolutions. The speed frame is an expensive machine in the spinning process as a whole, due to the complicated winding mechanism. In addition, the usual output from a speed frame is about 20-25 meters of roving yarn per minute. This low production cannot be increased in view of the winding system with flyers because a higher speed is limited by the centrifugal force which the flyers and roving bobbin must withstand.
Attempts have been made to bypass the use of the slubbing machine by direct spinning In this process, a ring-spinning machine is supplied with a fiber sliver. The high draft produced by sliver direct spinning only achieves the result to a restricted degree compared to that obtained with the supply of a flyer stubbing on a ring spinning machine. This is particularly true if fine yarns of 50 Nm and finer are being spun. In addition, the supply fiber slivers to ring-spinning machines is elaborate and complicated.
One possibility for replacing a speed frame slubbing machine is disclosed in the European Patent Application No. EP 375 242 A2. This publication describes a machine for the manufacture of a roving yarn from a fiber assembly which has a twist application means utilizing a rotating rotor. The rotor exhibits a continuous longitudinal hole on its axis of rotation, through which the fiber assembly that is to be rotated is guided. The rotor has at a specific height several holes arranged rotationally symmetrically. These radial holes connect the longitudinal hole with the outer surface of the rotor. The outer surface of the rotor is subjected to a vacuum or a strong under-pressure. As the fiber assembly is drawn through the longitudinal hole, individual free fiber ends are sucked off the surface of the fiber assembly into the radial holes. In operation, the rotor rotates while the fiber assembly is drawn through the longitudinal hole. The fiber ends located in the radial holes are wound around the moving fiber assembly. As a result, a rotation or true twist is applied to the fiber assembly. The device according to the process described is relatively expensive in manufacture and operation due to the mechanical elements (rotating rotor) and the vacuum technology.
De 32 37 989 C2 teaches the principle of drawing a fiber stubbing or drawing sliver in a drafting device and then applying a twist to the drawn fiber assembly. The application of the twist is effected by air jets in two sequential twist chambers. The application of the twist in the first pneumatic twist chamber is performed in a direction counter to the application of twist in the second pneumatic twist chamber. For example, the first twist application causes, a left-hand rotation, while the following twist application in the second twist chamber causes a right-hand rotation. A yarn manufactured in this manner is produced in accordance with what is known as the false twist process.
Patent Specification CH 617 465 teaches a false twist nozzle used for the manufacture of a staple fiber yarn, which is also a false twist spinning process. During the production of a yarn, the individual fibers are twisted together to the extent that the twisting is irreversible, and the yarn produced cannot be drawn any further. The strengthening achieved by the twisting is necessary because it is the only way the yarn will obtain the necessary high tensile strength. The consequence of this, however, is that the devices and spinning processes referred to are not suitable for forming a roving yarn. The roving yarn exhibits only what is referred to as a protective twist, which must not impede the further spinning processes on following machines, for example the process of drafting on ring-spinning machines. The devices described in these two aforementioned publications are therefore only suitable for the manufacture of yarns and are not suitable for manufacturing a roving yarn that remains capable of being drafted.
An object of the present invention is to provide a stubbing machine and method for the manufacture of a roving yarn that avoids the disadvantages referred above and exhibits the characteristics of conventional flyer slubbings or roving yarns.